<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40"><head><meta http-equiv=Content-Type content="text/html; charset=us-ascii"><meta name=Generator content="Microsoft Word 12 (filtered medium)"><style><!--
/* Font Definitions */
@font-face
        {font-family:"Cambria Math";
        panose-1:2 4 5 3 5 4 6 3 2 4;}
@font-face
        {font-family:Calibri;
        panose-1:2 15 5 2 2 2 4 3 2 4;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
        {margin:0in;
        margin-bottom:.0001pt;
        font-size:11.0pt;
        font-family:"Calibri","sans-serif";}
a:link, span.MsoHyperlink
        {mso-style-priority:99;
        color:blue;
        text-decoration:underline;}
a:visited, span.MsoHyperlinkFollowed
        {mso-style-priority:99;
        color:purple;
        text-decoration:underline;}
span.EmailStyle17
        {mso-style-type:personal;
        font-family:"Calibri","sans-serif";
        color:windowtext;}
span.EmailStyle18
        {mso-style-type:personal;
        font-family:"Calibri","sans-serif";
        color:#1F497D;}
span.EmailStyle19
        {mso-style-type:personal-reply;
        font-family:"Calibri","sans-serif";
        color:#0F243E;}
.MsoChpDefault
        {mso-style-type:export-only;
        font-size:10.0pt;}
@page WordSection1
        {size:8.5in 11.0in;
        margin:1.0in 1.0in 1.0in 1.0in;}
div.WordSection1
        {page:WordSection1;}
--></style><!--[if gte mso 9]><xml>
<o:shapedefaults v:ext="edit" spidmax="1026" />
</xml><![endif]--><!--[if gte mso 9]><xml>
<o:shapelayout v:ext="edit">
<o:idmap v:ext="edit" data="1" />
</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span style='color:#0D0D0D'>After learning about the Web Mercator Projection at the last SHRUG meeting – and being puzzled why ESRI called it a projection [not a simple variation on Decimal Degree], I had an application for this projection. The Blackboard Corporation is creating a web applet for FAMU, using map data I provided. I had converted my precise, state plane HARN map into WGS_1984. I gave them point [X,Y] data from the same projection. <o:p></o:p></span></p><p class=MsoNormal><span style='color:#0D0D0D'><o:p> </o:p></span></p><p class=MsoNormal><span style='color:#0D0D0D'>The day after the SHRUG meeting I was told my DD map did not line up. I guessed instantly that they were using Web Mercator. I projected the map to Web Mercator and they were happy. <o:p></o:p></span></p><p class=MsoNormal><span style='color:#0D0D0D'><o:p> </o:p></span></p><p class=MsoNormal><span style='color:#0D0D0D'>Then I was asked to create several more campus points: Campus Center, the Pool, Tennis Courts, other stuff. <o:p></o:p></span></p><p class=MsoNormal><span style='color:#0D0D0D'>I worked with the data in Web Mercator, then did a new “Add XY”, exported the data and didn’t look closely at it. I received complaints from the Blackboard people that it was in a different format. I checked – and they were right. Instead of -83.nnn, 30.nnn, it was in the format -93nnnn, 470nnn . More like UTM coords. After an unsuccessful call to ESRI about it, I Googled the alleged projection and discovered this: Web Mercator is used by Google, Bing and ESRI for world scale mapping. Here is the strange part: It creates a hybrid [or bastardized] DD-Cartesian coordinate system, outputting X,Y points in meters. ESRI has a ‘simple’ conversion showing how any point is converted. <o:p></o:p></span></p><p class=MsoNormal><span style='color:#0D0D0D'><o:p> </o:p></span></p><p class=MsoNormal><span style='color:#0D0D0D'>So, Web Mercator is a ‘projection’ of sorts, but it has limitations you may not expect, aside from low precision and distortion proportional to distance from the equator [although the math tries to reduce that]. I suppose it being called “Mercator” would have alerted a more clever person, but I missed it. The ESRI tech clearly had no idea of the relationship between DD and Web Mercator and no one had asked before. <o:p></o:p></span></p><p class=MsoNormal><span style='color:#0D0D0D'><o:p> </o:p></span></p><p class=MsoNormal><span style='color:#0D0D0D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:8.0pt;color:#0D0D0D'>William B. Porter <b>william.porter@famu.edu 850 412 5972<o:p></o:p></b></span></p><p class=MsoNormal><span style='font-size:8.0pt;color:#0D0D0D'>Application Coordinator for GIS / Infrastructure<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:8.0pt;color:#0D0D0D'>Florida A&M University<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:8.0pt;color:#0D0D0D'>EIT / GIS<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:8.0pt;color:#0D0D0D'>Perry-Paige, West Wing Ground floor,<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:8.0pt;color:#0D0D0D'>Office 1 -D<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:8.0pt;color:#0D0D0D'>1740 S. M L King BLVD<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:8.0pt;color:#0D0D0D'>TLH FL 32307<o:p></o:p></span></p><p class=MsoNormal><span style='color:#0F243E'><o:p> </o:p></span></p><p class=MsoNormal><span style='color:#0F243E'><o:p> </o:p></span></p></div></body></html>